Wireless communication systems have been diversified in order to provide various types of communication services such as voice or data service. In general, a wireless communication system is a multiple access system capable of sharing available system resources (bandwidth, transmit power or the like) so as to support communication among multiple users. Examples of the multiple access system include a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, a Single Carrier Frequency Division Multiple Access (SC-FDMA) system a Multi Carrier Frequency Division Multiple Access (MC-FDMA) system and the like.
Device-to-device (D2D) communication refers to a communication scheme for establishing a direct link between user equipments (UEs) and directly exchanging voice, data, etc. between the UEs without intervention of an evolved NodeB (eNB). D2D communication may include UE-to-UE communication, peer-to-peer communication, etc. In addition, the D2D communication scheme is applicable to machine-to-machine (M2M) communication, machine type communication (MTC), etc.
D2D communication has been considered as a method for solving burdens of an eNB due to rapid increase in data traffic. For example, in D2D communication, since data is exchanged between devices unlike an existing wireless communication system, network overload may be reduced. In addition, by introducing D2D communication, decrease in number of procedures performed in an eNB, decrease in power consumption of devices participating in D2D, increase in data transfer rate, increase in network capacity, load distribution, cell coverage enlargement, etc. may be achieved.